I can no longer access the files on my 32GB USB flash Drive

Hello and good morning to you all. I have a slight problem please. I have a 32gb usb flash drives which has been working flawlessly for the last few months....with my windows 7 laptop.and when I go to my computer it says 12.1GB free of 29.7GB,..then when i click on the drive it says this folder is empty!!! any suggestions please. I have kaspersky internet security 2012, and i did use this to scan it, but nothing came up.

But on thursday evening a friend inserted their usb flash drive into my laptop,..and kaspersky did detect a few viruses and neutralized them.

From another PC, copy the flash drive's files onto that machine. When confident the transfer is legit, copy the files back into the re-formatted flash drive. If the files are sensitive, ensure the transfer is legit and complete from your own PC, then remove from the other PC.